Interconnect structures for substrate

ABSTRACT

A device for use with integrated circuits is provided. The device includes a substrate having a through-substrate via formed therethrough. Dielectric layers are formed over at least one side of the substrate and metallization layers are formed within the dielectric layers. A first metallization layer closest to the through-substrate via is larger than one or more overlying metallization layers. In an embodiment, a top metallization layer is larger than one or more underlying metallization layers. Integrated circuit dies may be attached to the substrate on either or both sides of the substrate, and either side of the substrate may be attached to another substrate, such as a printed circuit board, a high-density interconnect, a packaging substrate, an organic substrate, a laminate substrate, or the like.

TECHNICAL FIELD

This disclosure relates generally to integrated circuits and, moreparticularly, to forming interconnect structures on interposers for usewith integrated circuits.

BACKGROUND

Since the invention of the integrated circuit (IC), the semiconductorindustry has experienced continued rapid growth due to continuousimprovements in the integration density of various electronic components(i.e., transistors, diodes, resistors, capacitors, etc.). For the mostpart, this improvement in integration density has come from repeatedreductions in minimum feature size, which allows more components to beintegrated into a given area.

These integration improvements are essentially two-dimensional (2D) innature, in that the volume occupied by the integrated components isessentially on the surface of the semiconductor wafer. Although dramaticimprovement in lithography has resulted in considerable improvement in2D IC formation, there are physical limits to the density that can beachieved in two dimensions. One of these limits is the minimum sizeneeded to make these components. Also, when more devices are put intoone chip, more complex designs are required.

In an attempt to further increase circuit density, three-dimensional(3D) ICs have been investigated. In a typical formation process of a 3DIC, two dies are bonded together and electrical connections are formedbetween each die and contact pads on a substrate. For example, oneattempt involved bonding two dies on top of each other. The stacked dieswere then bonded to a carrier substrate and wire bonds electricallycoupled contact pads on each die to contact pads on the carriersubstrate.

A substrate has been investigated for providing 3D IC packages. In thisattempt, a silicon die is attached to a substrate, such as aninterposer. The interposer may have through-substrate vias that are usedto provide an electrical connection between the integrated circuit dieon one side to electrical connections on the other side. Dielectriclayers may be formed over the through-substrate vias and metallizationlayers are formed in the dielectric layers, such as vias formed toprovide electrical connections between adjacent metallization layers. Inthis embodiment, the metallization layers and via sizes increase as themetallization layers extend away from the through-substrate vias.

This configuration, however, may experience open/shorting conditions inthe interconnect structure and/or de-lamination/cracking issues. Therelative volume of the through-substrate vias and the relativecoefficient of thermal expansion (CTE) as compared to the interconnectstructure may cause the through-substrate via to “pop” during thermalcycles. The popping of the through-substrate vias may then cause thelayers to delaminate or crack, as well as possibly causing a shorting oropen condition in the interconnect structure.

SUMMARY

A device for use with integrated circuits is provided. The deviceincludes a substrate having one or more through-substrate vias extendingthrough a substrate. A plurality of dielectric layers are formed over afirst side of the substrate, and a plurality of metallization layers areformed in the plurality of dielectric layers. A first metallizationlayer closest to the one or more through-substrate vias is larger thanone or more overlying metallization layers. In an embodiment, a topmetallization layer is larger than one or more underlying metallizationlayers. Integrated circuit dies may be attached to the substrate oneither or both sides of the substrate, and either side of the substratemay be attached to another substrate, such as a printed circuit board, ahigh-density interconnect, a packaging substrate, an organic substrate,a laminate substrate, or the like.

Other embodiments are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of an interconnect structure inaccordance with an embodiment;

FIG. 2 is a cross-sectional view of an interconnect structure inaccordance with another embodiment;

FIG. 3 is a cross-sectional view of an interconnect structure inaccordance with yet another embodiment; and

FIGS. 4 and 5 illustrate a substrate having two dies attached thereto inaccordance with embodiments.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments of the disclosure are discussedin detail below. It should be appreciated, however, that the embodimentsprovide many applicable inventive concepts that can be embodied in awide variety of specific contexts. The specific embodiments discussedare merely illustrative, and do not limit the scope of the disclosure.

A novel interconnect structure, which may be connected tothrough-substrate vias (TSVs), and the method of forming the same areprovided in accordance with an embodiment. The intermediate stages inthe manufacturing of the embodiment are illustrated. The variations ofthe embodiment are discussed. Throughout the various views andillustrative embodiments, like reference numbers are used to designatelike elements.

Referring first to FIG. 1, a portion of a first substrate 100 is shownin accordance with an embodiment. The first substrate 100 may be, forexample, a silicon or glass interposer, an organic substrate, a ceramicsubstrate, a high-density interconnect, or the like. In someembodiments, the first substrate 100 may include electrical elements,such as capacitors, resistors, signal distribution circuitry, and/or thelike. These electrical elements may be active, passive, or a combinationof active and passive elements. In other embodiments, the firstsubstrate 100 is free of electrical elements, including passive elementssuch as capacitors, resistors, inductors, varactors, or the like.

An interconnect structure 102, which includes dielectric layers 106 andmetallization layers 104, is formed on the first substrate 100. Vias 108interconnect the various metallization layers 104. The dielectric layers106 may be any suitable dielectric material. In an embodiment, one ormore of the dielectric layers 106 are formed of a material having a lowdielectric constant value (LK value), e.g., a k value less than about3.5, such as CVD Black Diamond-I, SOD SILK, or the like. In anotherembodiment, one or more of the dielectric layers 106 are formed of amaterial having an extremely low dielectric constant (ELK value), e.g.,a k value less than about 2.5, such as CVD Black Diamond-II.

The metallization layers 104 and the vias 108 may be formed of anysuitable conductive material using any suitable process. For example, inan embodiment a damascene process is utilized in which the respectivedielectric layer is patterned and etched utilizing photolithographytechniques to form trenches corresponding to the desired pattern ofmetallization layers 104 and/or vias 108. An optional diffusion barrierand/or adhesion layer is deposited and the trench is filled with aconductive material. Suitable materials for the barrier layer includestitanium, titanium nitride, tantalum, tantalum nitride, or otheralternatives, and suitable materials for the conductive material includecopper, silver, gold, tungsten, aluminum, combinations thereof, or thelike. In an embodiment, the metallization layers may be formed bydepositing a seed layer of copper or a copper alloy, and filling thetrench by electroplating. A chemical mechanical planarization (CMP) maybe used to remove excess conductive material from a surface of therespective dielectric layer 106 and to planarize the surface forsubsequent processing.

Through-substrate vias 110 are formed in the first substrate 100 toprovide an electrical connection between opposing sides of the firstsubstrate 100, as well as between an electrical element formed on thefirst substrate 100 and an external connection. The through-substratevias 110 may be formed by any suitable technique and of any suitablematerial(s). For example, the through-substrate vias 110 may be formedby etching a via partially through the substrate and depositing aconductive material therein, after which the backside of the substratemay be thinned to expose the through-substrate vias 110 on the backsideof the first substrate 100. In another technique, the through-substratevias 110 may be formed by etching a via partially through the firstsubstrate 100 and depositing a dielectric layer in the via. In thisembodiment, the dielectric layer within the via is removed after thebackside of the substrate is thinned, and a conductive material isre-deposited within the via.

The through-substrate vias 110 may be filled with a conductive materialsuch as Al, Cu, other metals, alloys, doped polysilicon, combinationsthereof, and the like. Furthermore, the through-substrate vias 110 mayhave one or more liners 112, such as a barrier layer, adhesion layer, orthe like, formed of a dielectric material, conductive material, or acombination thereof.

A thinning process may be performed on a backside of the substrate 100to expose the through-substrate vias 110. The thinning process may beperformed using an etching process and/or a planarization process, suchas a CMP process. For example, initially a planarizing process, such asa CMP, may be performed to initially expose the liner 112 of thethrough-substrate vias 110. Thereafter, one or more wet etchingprocesses having a high etch-rate selectivity between the material ofthe liner 112 and the first substrate 110 may be performed, therebyleaving the through-substrate vias 112 protruding from the backside ofthe first substrate 100 as illustrated in FIG. 1. In embodiments inwhich the first substrate 100 comprises silicon, the etch process maybe, for example, a dry etch process using HBr/O₂, HBr/Cl₂/O₂, SF₆/CL₂,SF₆ plasma, or the like.

After recessing the backside of the first substrate 100, a firstprotective layer 120, such as a spin-on glass (SOG) layer, is formed.Thereafter, one or more etching steps may be performed to recess thefirst protective layer 120 and to remove the liner, if present. Theetching processes may have a high etch-rate selectivity between thematerial of the first protective layer 120/liner 112 and the material ofthe through-substrate vias 112. It should be noted, however, that inother embodiments, the through-substrate vias 110 may not protrude fromthe backside of the first substrate 100. Any suitable configuration ofthrough-substrate vias 110 and the associated electrical connections maybe used.

A redistribution layer 122 and a second protective layer 124 may beformed over the first protective layer 120. The redistribution layer 122may be formed of any suitable conductive material, such as copper,copper alloys, aluminum, silver, gold, combinations thereof, and/or thelike, formed by any suitable technique, such as electro-chemical plating(ECP), electroless plating, other deposition methods such as sputtering,printing, and chemical vapor deposition (CVD) methods, or the like. Amask (not shown) may also be used.

The second protective layer 120 may be formed, for example, of a solderresist material or low-temperature polyimide deposited and etched backto expose a portion of the redistribution layer 122. The secondprotective layer 124 may be blanket formed and patterned to formopenings, in which under bump metallization (UBM) structures 126 areformed. The second protective layer 124 may be formed of nitrides,oxides, polyimide, low-temp polyimide, solder resist, and/or the like.The openings in the second protective layer 124 may be formed usingphoto-lithography techniques such that the openings expose portions ofthe redistribution layer 122. The UBM structures 126 are formed of oneor more layers of conductive materials and provide an electricalconnection between the redistribution layer 122 and the solderbumps/balls 128 to be formed in subsequent processing steps. The UBMstructures 126 may be formed, for example, of one or more layers ofchrome, a chrome-copper alloy, copper, gold, titanium, titaniumtungsten, nickel, combinations thereof, or the like. It should be notedthat the first protective layer 120 and/or the second protective layer124 may act as a stress buffer layer to reduce the amount of stress inthe electrical connections.

Layers similar to the first protective layer 120, the redistributionlayer 122, the second protective layer 124, and the UBM structures 126may be formed over the interconnect structure 102, using similarprocesses and materials as discussed above to provide an electricalconnection to contacts in the uppermost metallization layer (e.g., thetop metal TM layer).

It should also be noted that a carrier substrate (not shown) may beattached to one side of the first substrate 100 while processing theopposing side of the first substrate 100 to provide temporary mechanicaland structural support during processing and to reduce or prevent damageto the substrate. The carrier substrate may be attached using anadhesive, such as an ultraviolet (UV) glue, which loses its adhesiveproperty when exposed to UV lights.

As noted above, the volume of the through-silicon vias is largerelatively compared to the interconnect structure. And, as a result, theCTE mismatch between the material of the through-substrate vias and thesubstrate causes considerable stress as the device experiencestemperature cycles. The stress may in turn cause the through-substratevia interconnect issues such as through-substrate via popping, which inturn may cause an electrical open/short failure conditions in theinterconnect structure or cause delamination of one or more of thedielectric layers.

It has been found that structuring the interconnect layers asillustrated in FIG. 1 may reduce the amount of stress in theinterconnect structure 102, thereby reducing or preventing theelectrical open/short failure condition and/or delamination issues. Inparticular the dimensions of the metallization layers are varied suchthat the first metallization layer (indicated in figures by M1) isrelatively larger than in previous systems. By enlarging the firstmetallization layer M1, the pop-up height of the through-substrate viais not likely to cause a failure in the first metallization layer M1.Furthermore, the larger dimension of the first metallization layer M1allows more thermal budget before M1 metallization, which can avoidfurther popping of the through-substrate via during the processing ofthe overlying metallization layers M2˜TM thermal cycles. For example,when the first metallization layer M1 is thicker than the pop-up heightof the through-substrate via, more thermal budget in advance allows thepop-up height to saturate and the maximum height can be covered by thefirst metallization layer M1. Because the pop-up height of thethrough-substrate via is saturated by applying enough thermal budget atthe first metallization layer M1, further popping of thethrough-substrate via will be prevented or reduced during fabrication ofthe metallization layers M2˜TM.

In an embodiment, the first metallization layer M1 is larger than one ormore of the overlying metallization layers (indicated in figures by M2,M3, . . . , TM). In the particular embodiment illustrated in FIG. 1 inwhich there are three metallization layers, e.g., M1, M2, and TM, thefirst metallization layer M1 is the largest metallization layer. Inother embodiments, however, the first metallization layer M1 may notnecessarily be the largest, though it is desired that one or more of themetallization layers between the first metallization layer M1 and thetop metallization layer TM is smaller than both the first metallizationlayer M1 and the top metallization layer TM.

It should be noted when discussing one metallization layer being largerthan another metallization layer, the relative dimension may be thethickness T, width W, or both.

Furthermore, FIG. 1 illustrates three metallization layers forillustrative purposes only, and accordingly, other embodiments may havemore metallization layers. For example, FIGS. 2 and 3 illustrateembodiments that have four metallization layers and five metallizationlayers, respectively, wherein like reference numerals refer to likeelements. With regard to FIG. 2, the second metallization layer M2 issmaller than all of the other metallization layers. In anotherembodiment similar to FIG. 2, the relative sizes of the secondmetallization layer M2 and the third metallization layer M3 may bereversed, such that the third metallization layer M3 is the smallestmetallization layer.

FIG. 3 illustrates an embodiment having five metallization layers inwhich the third metallization layer M3 is the smallest. In otherembodiments, the second metallization layer M2 or the thirdmetallization layer M3 may be the smallest metallization layer, suchthat both the first metallization layer M1 and the top metallizationlayer TM are larger than all of the other metallization layers.

FIGS. 4 and 5 illustrate embodiments in which the first substrate 100 iselectrically coupled to a first die 400, a second die 420, and a secondsubstrate 440. The first die 400 and the second die 420 may be anysuitable integrated circuit die for a particular application. Forexample, one of the first die 400 and the second die 420 may be a memorychip, such as a DRAM, SRAM, NVRAM, and/or the like, while the other diemay be a logic circuit. As one of ordinary skill in the art willappreciate, in this embodiment the conductive bumps connecting the firstsubstrate 100 to the second substrate 400 are greater than a thicknessof the second die 420, such that there will be sufficient space betweenthe first substrate 100 and the second substrate 440 for the second die420.

FIGS. 4 and 5 also illustrate an underfill material 450 placed betweenthe various components, e.g., the first die 400, the second die 420, thefirst substrate 100, and the second substrate 440. An encapsulant orovermold, such as a top insulating material (TIM) 452, may also beformed over the components to protect the components from theenvironment and external contaminants. An additional overmold may alsobe formed completely encompassing the first die 400.

Also illustrated in FIGS. 4 and 5 is a dummy substrate 454. While notproviding electrical components, the dummy substrate may be desirable toaid in the dissipation of heat from the first substrate 100, therebymaintaining the first substrate 100, and hence the first die 400 and thesecond die 420 at a lower operating temperature. The lower operatingtemperature further reduces the variance in the temperature of thethrough-substrate vias and may further reduce or prevent failures due totemperature cycling of the through-substrate vias.

The second substrate 440 may be any suitable substrate, such as anorganic substrate, a 1/2/1 laminate substrate, a 4-layer laminatesubstrate, a printed circuit board, a high-density interconnect board, apackaging substrate, or the like.

As one of ordinary skill in the art will appreciate, the embodimentillustrated in FIG. 4 places the interconnect structure 102 face down,or towards the second substrate 440, and the embodiment illustrated inFIG. 5 places the interconnect structure face up, or away from thesecond substrate 440. It should be noted that these embodiments areprovided for illustrative purposes only and in yet another embodiment,an interconnect structure similar to the interconnect structure 102discussed above may be placed on both sides of the substrate.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the embodiments as defined by the appended claims. Moreover,the scope of the present application is not intended to be limited tothe particular embodiments of the process, machine, manufacture, andcomposition of matter, means, methods and steps described in thespecification. As one of ordinary skill in the art will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the disclosure.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps. In addition, each claim constitutes a separateembodiment, and the combination of various claims and embodiments arewithin the scope of the disclosure.

What is claimed is:
 1. A device comprising: a substrate having a firstside and a second side; a through-substrate via extending through thesubstrate from the first side to the second side; a plurality ofdielectric layers over at least one of the first side and the secondside; and a plurality of metallization layers formed in the plurality ofdielectric layers and comprising a first metallization layer being incontact with the through-substrate via, the first metallization layerhaving a thickness larger than one or more overlying metallizationlayers, and the first metallization layer thickness being greater than apop-up height of at least one through-substrate via, wherein each one ofthe plurality of metallization layers has a different thickness thanadjacent ones of the plurality of metallization layers; wherein theplurality of metallization layers comprises a top metallization layerwith an overlying passivation layer, the top metallization layer beinglarger than one or more underlying metallization layers.
 2. The deviceof claim 1, wherein one or more of the dielectric layers has adielectric constant less than 3.5.
 3. The device of claim 1, wherein oneor more of the dielectric layers has a dielectric constant less than2.5.
 4. The device of claim 1, wherein a top metallization layer and thefirst metallization layer are larger than the other metallizationlayers.
 5. The device of claim 1, further comprising a first dieattached to the first side.
 6. The device of claim 1, wherein thesubstrate comprises a silicon interposer.
 7. The device of claim 5,further comprising a second die attached to the second side.
 8. A devicecomprising: a first substrate having a first side and a second side, thefirst substrate having one or more through-substrate vias extendingthrough the first substrate; a plurality of dielectric layers over thefirst side of the first substrate; and a plurality of metallizationlayers, each of the plurality of metallization layers being in one ofthe plurality of dielectric layers and having a different thickness thanadjacent ones of the plurality of metallization layers; adjacentmetallization layers being electrically coupled by one or more vias, afirst metallization layer of the plurality of metallization layers beinga metallization layer closest to the one or more through-substrate vias,the first metallization layer having a thickness greater than athickness of one or more overlying metallization layers, and the firstmetallization layer thickness being greater than a pop-up height of atleast one through-substrate via; wherein a top metallization layer ofthe plurality of metallization layers is a metallization layer furthestfrom the one or more through-substrate vias with an overlyingpassivation layer, the top metallization layer being larger than one ormore underlying metallization layers.
 9. The device of claim 8, furthercomprising a first die attached to the first side and a second dieattached to the second side.
 10. The device of claim 9, furthercomprising a second substrate attached to the second side.
 11. Thedevice of claim 8, wherein one or more of the plurality dielectriclayers has a dielectric constant less than 3.5.
 12. The device of claim8, wherein one or more of the plurality of dielectric layers has adielectric constant less than 2.5.
 13. The device of claim 9, furthercomprising a second substrate coupled to the first side of the firstsubstrate.
 14. A method of forming a device, the method comprising:providing a first substrate having a through-substrate via extendingtherethrough; forming a first metallization layer in a first dielectriclayer on a first side of the first substrate, the first metallizationlayer being in direct contact with the through-substrate via, the firstmetallization layer having a first thickness; and forming metallizationlayers M2-Mn in respective ones of a plurality of dielectric layers overthe first metallization layer, wherein n is greater than 2, the firstthickness of the first metallization layer being greater than athickness of the metallization layers M2-Mn, and the first metallizationlayer thickness being greater than a pop-up height of at least onethrough-substrate via, wherein each of the metallization layers M2-Mnhave a different thickness from each other; wherein the metallizationlayer Mn is larger than metallization layers M2-M(n−1) and has apassivation layer covering a majority of an upper surface.
 15. Themethod of claim 14, further comprising: attaching a first die to thefirst side of the first substrate; attaching a second die to a secondside of the first substrate; and attaching a second substrate to thefirst side of the first substrate.
 16. The method of claim 14, furthercomprising: attaching a first die to the first side of the firstsubstrate; attaching a second die to a second side of the firstsubstrate; and attaching a second substrate to the second side of thefirst substrate.
 17. The method of claim 14, wherein one or more of theplurality of dielectric layers has a dielectric constant less than about3.5.